INDIANAPOLIS (AP) _ An Indianapolis prosecutor says the investigation into an explosion that killed a young couple and decimated their neighborhood is a “painstaking” process with no timetable for a resolution.
 
  Marion County Prosecutor Terry Curry told The Associated Press police are conducting interviews based partly on input from the public as investigators continue to seek the cause of the Nov. 10 blast that killed Jennifer and John Longworth. Thirty-three houses are to be demolished.
 
  Experts say explosions and arson cases can take years to close. The Federal Bureau of Investigation reports less than 20 percent of more than 43,000 arsons ended in arrests in 2011.
 
  Indianapolis terrorism consultant Peter Beering tells The Indianapolis Star such cases are the hardest to prove because investigators must determine what caused the crime and who’s responsible.